It is known to couple electrical signals to conductive traces formed on PCBs by means of permanently mounted electrical connectors mechanically and electrically attached to the PCB. The PCBs on which such electrical devices are mounted are provided with terminal pads or bores which form part of the PCBs. The electrical devices are provided with contacts or leads which are configured and positioned to be placed in overlying alignment with the terminal pads or bores. Generally, the pads are coated with a solder paste composition and, after the contact portions of the contacts or leads are placed into engagement with appropriate terminal pads, the solder paste composition is reflowed to thereby obtain a secure electrical engagement between each contact portion and its respective terminal pad.
Electrical connector devices are also mechanically connected to the substrates, generally by fasteners, such as mounting posts, hold downs, board locks, etc., that are inserted into corresponding openings formed in the PCB. These fasteners are typically used to align and secure the electrical connector in a predetermined position. The fasteners also hold the connectors in place for soldering, such that the solder tails remain inside the bores (or in position against the pads) of the PCB during solder reflow or other operations. In addition, the fasteners reduce stresses on the solder joints of the mounted components.
The fasteners are typically coupled to a connector using various techniques. Known fasteners for holding connector bodies against the surface of a PCB include top-actuated eyelets, heat stakes, screws, rivets, non-metallic posts, plastic snap fit pegs, pinch eyelets, nuts and bolts, and barbed press-fit hold downs for securing the connector to the PCB. Such fasteners typically extend through or engage a hole formed in the PCB.
These convention fasteners, however, typically exhibit a high insertion force in order to insert the fastener into the opening in the PCB making mounting of the electrical connector onto the surface of the PCB difficult. In addition, many of the conventional fasteners exhibit a low retention force between the fastener and the side walls of the opening in the PCB which results in the electrical connector becoming loosened or dislodged from the surface of the PCB.
Another drawback to certain styles of conventional fasteners is that, in order to develop sufficient retention force, some fasteners are designed to pass through a hole in the PCB and protrude through the opposite surface. For example, one style of non-metallic post is passed through a hole in the surface of the board and "staked," or deformed, to form a plug on the opposite surface. Still further, fasteners with hooked ends will snap into engagement with the underside of the board, causing many small components that are placed on the solder paste prior to reflow to be jarred from their pads. In addition, the fasteners must be specially sized for each application, having an appropriate diameter corresponding to the diameter of the opening in the printed circuit board, and a length corresponding to the board thickness. This adds costs and complexity to the fastener and the assembly process.
Another proposed style of fastener is anon-metallic post which is press fit into a hole in the board. Unlike those previously discussed, press fit fasteners need not protrude through the opposite surface of the board. Unfortunately, many press fit fasteners require insertion forces which may preclude their insertion by hand tools. Furthermore, such fasteners are very sensitive to tolerance stack-ups between the hole diameter and the fastener diameter.
Other known fasteners have a body design that requires some type of forming operation during the manufacturing process. This forming operation adds complexity and costs to the manufacturing of the fastener.
Accordingly, there remains a need for a fastener having the characteristics of a low insertion force and at the same time a sufficient retention force to hold down various connectors to a substrate. There remains a further need for such a fastener which also provides an efficient way to align the contact terminals on the connector with which it is used with their respective mounting apertures on the substrate